"It turns out that the only reason the astronauts saw the Earth when they did was because Frank Borman, the mission commander, was in the process of rotating the spacecraft — which was pointing nose down at the moon," Chaikin tells NPR.

"It just so happens that as they came around, Bill Anders, the rookie on the flight over on the right side of the spaceflight, could see the Earth coming up in his window. This had happened three previous times on Apollo 8, but they weren't in position to see it," he says.

Aboard Apollo, Anders is the first to see the potential shot: "Oh, my God, look at that picture over there," he can be heard saying. "There's the Earth coming up. Wow, is that pretty!"

But what happened next will sound familiar to anyone who remembers the days before digital cameras:

Lovell hands him the film just as Anders is heard saying, "I think we missed it."

But within seconds, Lovell sees the shot again in another window of the command module. He asks for the camera from Anders, who seems a bit defensive at having his role as mission photographer usurped.

Anders: "Wait a minute, just let me get the right setting here now, just calm down. Calm down, Lovell!"

Anders then gets the shot that has been reproduced thousands of times all over the world in the past 45 years.

"It sounds incredible to us to think, 'Weren't they looking for [the Earth] when they got to the moon?' " Chaikin tells NPR. "But as Bill Anders explained to me many years later, he said, 'Look, we were trained to go to the moon. We were focused on the moon, observing the moon, studying the moon, and the Earth was not really in our thoughts until it popped up above that horizon."

Meanwhile, on Monday, Lovell re-enacted another memorable moment from the groundbreaking mission: a Christmas Eve broadcast from lunar orbit. Lovell, Borman and Anders took turns reading from the Book of Genesis.

Lovell ended his re-enactment with the same closing the trio used on Dec. 24, 1968:

"From the crew of Apollo 8, we close with good night, good luck, a Merry Christmas and God bless all of you, all of you on the good Earth."

Correction at 10:35 a.m. ET, Dec. 24: We initially wrote that Anders saw the moon coming up in his window. But as commenter "leew261" noted, it was the Earth that Anders saw rising. We've corrected the wording above.

Copyright 2014 NPR. To see more, visit http://www.npr.org/.

Transcript

DAVID GREENE, HOST:

Christmas Eve 45 years ago, three men became the first human beings to orbit the moon.

JIM LOVELL: For all the people back on Earth, the crew of Apollo 8 has a message that we would like to send to you.

GREENE: As they passed over the gray, dusty and cratered surface of the moon, astronauts Jim Lovell, Frank Borman and Bill Anders, read from the book of Genesis.

LOVELL: In the beginning, God created the heaven and the Earth. And the earth was without form and void, and...

GREENE: That broadcast you're hearing had a powerful impact on the planet more than 200,000 miles away from the tiny Apollo spacecraft. Here to talk that moment and a famous photo snapped that night in 1968, is space and science writer, Andrew Chaikin. Good morning, Andy.

ANDREW CHAIKIN: Good morning.

GREENE: So, take me back to 1968. Where were you that night?

CHAIKIN: Well, I was 12 years old and I was in my parents' bedroom in front of the old black and white Zenith, sharing what the world was sharing at that moment in this mind-blowing experience of hearing human voices coming to us from orbit around the moon.

GREENE: Well, 12 years old - I mean, you were young but old enough to know that 1968 was just an awful year in the United States. Robert Kennedy was assassinated, Martin Luther King was assassinated, the Vietnam War protests were raging. I mean, what a moment for this to happen.

CHAIKIN: It's true, and it's only as an adult that looking back, I can see just what a turning point that was for the whole country after going through those traumas, to actually have this transcending experience.

GREENE: There was an iconic photo from that mission that shows, I guess the best way to describe it, I mean, it's the earth almost rising above the surface of the moon. Because you see just the top part of the earth lit. And, you know, even 45 years later that image is in a lot of places - posters and stamps. You've been looking at this photo and finding out some more details about it.

CHAIKIN: Yes. The earth rise photo came about by accident. A fellow at NASA's Goddard Space Flight Center in the scientific visualization studio - a fellow named Ernie Wright - went back to the astronaut's photography and compared it with new data from the lunar reconnaissance orbiter, which has been circling the moon since 2009. It has absolutely superb cameras. And Ernie was able to go back to the astronaut's photographs and figure out where, exactly, over the moon Apollo 8 was at the moment the Earth appeared. And it turns out Frank Borman, the mission commander, was in the process of rotating the spacecraft. And it just so happens that as they came around, Bill Anders could see the Earth coming up through his side window. This had happened three previous times on Apollo 8 but their windows were facing away from the Earth. So, it wasn't until Borman made this maneuver that they actually could see it for the first time. And I got to tell you one little human moment that came about that Anders told me about when he saw the Earth coming up. He said his mind was sort of divided between my God that's the prettiest thing I'd ever seen, and thinking about having to get back there. And he thought to myself, my God, I hope we hit that thing.

GREENE: Well, Andy, thanks so much for remembering this moment with us.

CHAIKIN: I've really enjoyed it. Thank you.

GREENE: That's Andrew Chaikin. He's author of "A Man on the Moon: The Voyages of the Apollo Astronauts."

LOVELL: And from the crew of Apollo 8, good night, good luck. Merry Christmas and God bless all of you, all of you on the good Earth.

GREENE: And you can watch a NASA video about that iconic photograph on the NPR blog The Two Way. Transcript provided by NPR, Copyright NPR.